A tilt rotor aircraft can have wing mounted rotatable nacelles that can be selectively rotated between a helicopter mode and an airplane mode. In the helicopter mode, the nacelles can be rotated to an approximate vertical position so that the tilt rotor aircraft can take off, land, and hover similar to a conventional helicopter. In the airplane mode, the nacelles can be rotated to an approximate horizontal position so that the tilt rotor aircraft can fly similar to a fixed wing aircraft.